1. Field of the Invention
The present invention relates to a piezoelectric element and piezoelectric element manufacturing method and an actuator using a piezoelectric element manufactured by said method.
2. Description of the Related Art
Actuators using a piezoelectric element have been widely used in recent years in cameras, measurement devices, and other precision mechanisms used for positioning and driving driven members because they increase the conversion efficiency for converting the supplied electrical energy to a drive force, increase the generated drive force while reducing the form-factor and weight, and allow the drive force to be easily controlled.
The piezoelectric element used as a power source in such actuators are constructed as units of multilayered piezoelectric elements, as disclosed in U.S. Pat. No. 5,589,723. This construction adds the displacement in the thickness direction generated in the piezoelectric element unit so as to take the largest possible displacement.
The piezoelectric element constructed as a plurality of layers of the piezoelectric element unit is subject to higher cost because it is manufactured by complex operations involving a process for providing electrodes on the respective surfaces of the unit elements, a process for adhering the laminate layers, and a process for connecting the leads of the electrodes of each layer.
A piezoelectric element formed as a single layer of a hollow cylinder has been proposed as another configuration of a piezoelectric element in U.S. Pat. No., 4,874,979.
The hollow cylinder piezoelectric element characteristically has a relatively high mechanical strength, but requires a higher electric field strength to increase the generated displacement. Accordingly, when there is a restriction on the voltage applied to the piezoelectric element, the electric field intensity must be increased by making the piezoelectric element thinner. This arrangement is disadvantageous in that the strength of the piezoelectric element is reduced when attempting to increase the generated displacement.
For this reason, the present inventors considered constructing a piezoelectric element by forming a ceramic material having PZT (PbZrO3.PbTiO3) as a main component into a thin sheet, attaching electrodes to both surfaces, and wrapping the sheet into a cylindrical shape, then sintering the material.
The element of this construction is subject to disadvantages such as deformation of the piezoelectric element due to the heating process during sintering.